Sunday, January 22, 2017

Geometric Relationships: Circle, Sphere, and Equilateral Triangle

Geometric Relationships: Circle, Sphere, and Equilateral Triangle

Circle:  Relationship between Area and Circumference

We know that π is a constant (π ≈ 355/113, but more accurately, π ≈ 3.141592654).  And:

Circumference of a Circle:  C  = 2 * π * r
Area of a Circle: A = π * r^2

Observe that:
C = 2 * π * r
π = C / (2 * r)

And:
A = π * r^2
π = A / r^2

Hence:
C / (2 * r) = A / r^2
(2 * r) / C = r^2 / A
A * 2 * r = r^2 *C
A = C * r / 2

Sphere:  Relationship between Area and Circumference

Volume of a Sphere:  V = 4/3 * r^3 * π
Surface Area of a Sphere:  S = 4 * π * r^2

Solving for π:

V = 4/3 * r^3 * π
3 * V = 4 * r^3 * π
π = (3 * V) / (4 * r^3)

And:

S = 4 * π * r^2
π = S / (4 * r^2)

Then:
(3 * V) / (4 * r^3) = S / (4 * r^2)

Multiply both sides by 4 * r^2:
S = 3 * V / r


Equilateral Triangle:  Relationship between Perimeter and Area


Let a (small a) be the length’s side.   Then the area of the triangle:

A = 2 * (1/2 * a/2 * √3/2 * a) = a^2 * √3/4

With the perimeter:  P = 3 * a,

P = 3 * a
P^2 = 9 * a^2
a^2 = P^2 / 9

And

A = a^2 * √3 / 4
a^2 = 4 * A / √3

P^2 / 9 = 4 * A / √3
A = P^2 * √3 / 36

To summarize:

Circle:  Area and Circumference:  A = C * r / 2
Sphere:   Volume and Surface Area:  S = 3 * V / r
Equilateral Triangle:  Area and Perimeter:  A = P^2 * √3 / 36

The next blog will cover Platonic solids.  At least that’s the plan.  Have a great rest of the weekend.  

Eddie

This blog is property of Edward Shore, 2017.

Thursday, January 19, 2017

Retro Review: TI-60X

Retro Review: TI-60X

TI-60X.  Yes I forgot the multiplication sign here.

Company:  Texas Instruments
Years:  1991 – 1995? 2000?
Year of my TI-60X:  1991 (specifically week 46, November 1991)
Type:  Scientific, Formula Storage
Number of Steps: 96, shown in units of registers (12 registers of 8 steps each)
Operating System: Algebraic
Memory Registers: 12 (A through I, X, Y, Z)
Regressions Available:  Linear

Chipset:  Toshiba T9838
Battery: 1 CR2032

My late Uncle Ralph bought a TI-60X for me in 1992 (I think it was in ’92).  It was my first year of high school.  Uncle Ralph encouraged my love for calculators. (Thanks for all you did for me Uncle)

A Rich Feature Set

The TI-60X operates in Algebraic mode.  Simply, type in the expression as its written, and press [ =/ENTER ]. 

The TI-60X isn’t programmable in the traditional sense (keystroke or BASIC) but rather you can store formulas (A = π * B^2, for example) for later use.  I think the TI-60X is the first of its kind to store formulas.  Today, formula storage is a feature of the Sharp EL-520W.  More on this later.

You have your standard linear regression capabilities.  However, instead of the usual labels a, b, and r, you have ITC (intercept), SLP (slope), and COR (correlation) respectively.  If find these labels much helpful since calculators sometimes tend to switch the roles of a and b in linear regression mode.  Entry is rather easy, just enter the data point and press [ Σ+ ] and you are good to go.  No separate declaration of stats mode needed.

Equation:  y = INT + SLP * x

The Base conversions are on the TI-60X as well.  We also get the logical functions AND, OR, XOR, XNOR, NOT, and 2’s (compliment).  The TI-60X distinguishes the variables A-F from the hexadecimal A-F by assigning the latter set to the 3rd functions of the reciprocal, square, square root, and the trigonometric keys.  On the screen, hexadecimal letters are in bold while storage registers are not.

Fractions are included, as well as the decimal to/from fraction conversion.  The TI-60X has the following additional conversions:

* degrees, decimal-minute-seconds
* polar, rectangular coordinates
* inches, centimeters
* gallons, liters (litres)
* pounds, kilograms
* degrees Fahrenheit (°F), degrees Celsius (°C)

The Blocky Display


Can we talk about the display for a moment?  The text on the TI-60X’s screen is blocky.  According to the Datamath Calculator Museum, the character layout is 5 x 4 dots instead of the usual 7 x 5.  This display could be a throwback to the calculator display of the 1970s and 1980s where the numbers were made of linear segments. 

The article from Datamath on the TI-60X:  http://www.datamath.org/Sci/Modern/TI-60x.htm 

Formula Programming, Simultaneous Equations, and Integration

Up to 12 formulas can be stored, and they can have the labels A, B, C, D, E, F, G, H, I, X, Y, and Z.  The formulas can have more than one variable. Pressing [SOLVE] allow the user to calculate the formula, with each independent variable being prompted.  If there is a numerical value in the independent variable, the TI-60X will display it as a default choice. 

When the “SOLVE YN?” and “REVIEW YN?” prompts appear, the plus key acts as NO and the equals keys acts as YES. 

Integration is pretty easy.  At the appropriate prompted variable, press [2nd] [ , ] (dx) to insert the dx indicator.  You will be asked for a lower limit, upper limit, and the number of intervals.  I am assuming Simpson’s method but I’m not 100% sure.

Simultaneous equations of 2 x 2 and 3 x 3 linear systems are offered.  Execution takes up 2 or 3 registers respectively.   Solutions are stored in X, Y, and for 3 x 3 systems, Z. 

Example: y = 2 * x * sin x

Enter the formula:
Change to Radians mode by pressing [3rd] [LOG] (DR>) until the R indicator is displayed. 

Press [2nd] [ EE ] (FMLA).  At the “NAME?” prompt, press [ ( ] for Y (ALPHA is automatically turned on at this point) and enter the equation.

Calculate y(π/3).  Press [SOLVE].  At X, enter π/3.  Result:  Y = 1.813799364.

Integrate y(x) from 0.5 to 1, use 20 intervals.  Call up the Y= formula again, press [SOLVE].  At the X= prompt, clear the number and enter dx.  Enter the required parameters.  After calculation, the TI-60X displays Y = 0.521068842.  The integral is now stored in Y.

Final Verdict

For what it’s set out to do, the TI-60X accomplishes it rather well.  The calculator is rich with features and there is some storage for some formulas.  I also like the bolder blocky numbers in the display, they are easier to read.  I think the TI-60X launched the advanced scientific calculator genre which is now common place. 

Yes, this calculator is worth collecting.  I’m not sure what the prices are to purchase a used on from eBay, Amazon, or other shopping website, but I imagine it’s not expensive.  (I think the 60X was about $30-$40 when it was sold new back in the 1990s). 

Thank you for comments and support.  Until next time,

Eddie

This blog is property of Edward Shore, 2017.

Monday, January 16, 2017

Fun with the Sharp EL-5500 III

Fun with the Sharp EL-5500 III


Even though the EL-5500 III has one programming space, we can fit many programs in it.  One of the great features is that how programs take relatively little space.  Obviously you can change the line numbers, the sequence of lines are most important.

Euclid Algorithm – RUN 10

10 PAUSE “GCD: A>B”
18 INPUT “A: “; A, “B: “; B
20 C = A – INT(A/B)*B
30 IF C = 0 THEN 40
32 A = B
34 B = C
36 GOTO 20
40 PRINT “GCD = “; B
46 END

My first program on the EL-5500 III.  We can probably make the coding more efficient.  PRINT with a proceeding WAIT pauses execution until [ ENTER ] is pressed.

The command END ends the program execution and allows the space to have more than one routines.

Examples:
A: 100, B: 20.  Result:  GCD = 20
A: 63, B: 60.  Result:  GCD = 3

Binomial Expansion – RUN 50

50 PAUSE “(Ax + B)^n”
55 INPUT “A: “;A, “B: “;B, “N: “,N
60 FOR I=0 TO N
65 C = FACT(N) / (FACT(I) * FACT(N-I))
70 T = C * A^(N-I) * B^I
75 PRINT T; “*x^”; N-I
80 NEXT I
85 END

The command PAUSE shows the text for about 0.85 seconds.

This program displays each coefficient one at time.

Example:  A = 3, B = -2, N = 3.  Expand (3 – 2x)^3.
Result:  27, -54, 36, -8  (27x^3 – 54x^2 + 36x – 8)

Days Between Dates – RUN 100

100 PAUSE “Days between Dates”
112 INPUT “M1:”; M1, “D1:”; D1, “Y1:”; Y1
113 INPUT “M2:”; M2, “D2:”; D2, “Y2:”; Y2
115 M = M1: D = D1: Y = Y1
117 GOSUB 140
119 F1 = F
121 M = M2: D = D2: Y = Y2
123 GOSUB 140
125 F2 = F
127 N = F2 – F1
129 PRINT “# DAYS: “; N
131 END
140 IF M > 2 THEN 150
142 X = 0: Z = Y – 1
144 GOTO 160
150 X = INT(.4 * M + 2.3): Z = Y
160 F = 365 * Y + 31* (M – 1) + D + INT(Z/4) – X
165 RETURN

If I had it my way, every calculator that isn’t a basic 4-function calculator will have a Days Between Dates function.

Example:  November 4, 1986 to January 12, 2017
M1:  11, D1: 4, Y1: 1986 
M2: 1, D2: 12, Y2: 2017
Result:  11,027

Power of a Complex Number – RUN 200

This calculates (a + bi)^n

200 PAUSE “(A + Bi)^n”
203 INPUT “A: “;A, “B: “;B, “n: “;N
205 IF A<>0 THEN 210
207 A = A^N: GOTO 220
210 R = √(A^2 + B^2)^N
212 T = ATN(B/A)*N
214 A = R * COS T
216 B = R * SIN T
220 PRINT A; “+”; B; “i”
225 END

The command <> means not equals (≠) and ATN is the arctangent function.

Examples:
(2 + 3i)^3:  A = 2, Bi = 3.  Result: -46 + 9i
(-5 + i)^2:  A = -5, Bi = 1.  Result: 24 – 10i

Error Function Approximation – RUN 250

250 PAUSE “APPROX ERF(X)”
252 CLEAR
254 DIM A(3)
256 E = 0
260 INPUT “X > 0 : “; X
262 T = RCP(1 + .47047 * X)
270 FOR I = 1 TO 3
272 READ A(I)
274 E = E + A(I) * T^I
276 NEXT I
280 DATA .3480242, -.0958798, .7478556
290 E = 1 – E * EXP(-(X^2))
292 PRINT “ERF : “, F
294 CLEAR
296 END

Use the command CLEAR to clear all the variables.  At this point, I will use this command both at the beginning and end of calculations.  The command RCP is the reciprocal.  Finally, EXP is from e^x function, not the [EXP] key.

Example:
x = 0.53, erf ≈ 0.546455764
x = 0.88, erf ≈ 7.86708E-01 = 0.786708

Keep in mind this approximation is accurate 2.5 parts in 10^-5.

Source:  Smith, Jon M.  Scientific Analysis on the Pocket Calculator  John Wiley & Sons: New York. 1975.  ISBN 0-471-79997-1

Simpson’s Rule – RUN 300

Calculates the numeric integral ∫ f(x) dx from x = L to x = U.

You can edit the function at line 342.  In BASIC-PRO mode, call up line 342 by LIST 342.  Edit as desired.

300 PAUSE “Simpsons Rule”
302 CLEAR
304 INPUT “LOWER: “; L, “UPPER: “; U, “PARTS (even): “; N
306 RADIAN
308 X = L: GOSUB 340: T = F
310 X = U: GOSUB 340: T = T + F
314 H = (U – L)/N
320 FOR I = 1 TO N-1
322 X = L + I * H: GOSUB 340
324 R = I/2 – INT(I/2)
326 IF R = 0 THEN LET T = T + 2*F
328 IF R <> 0 THEN LET T = T + 4*F
330 NEXT I
332 T = T * H/3
334 PRINT “Integral: “, T
336 CLEAR
338 END
340 REM f(x)
342 F = [insert f(X) here]
344 RETURN

Note:  I finally learn why LET is included in BASIC.  In an IF-THEN statement, if you want to assign a value or calculation to a variable, you will need a LET command.

I use a REM (remark) command on line 340.  REM is for comments and nothing said after REM is executed.

Examples:

342 F = X^2 – 1
L = -2, U = 2, N = 14.  Result:  1.333333334 (Actual: 4/3 ≈ 1.333333333)

342 F = √(X – 1)
L = 2, U = 3, N = 14.  Result: 1.218951372 (Actual:  ≈ 1.2158951416)

Dancing Star Demo – RUN 400

400 PAUSE “Dancing Star Demo”
405 CLEAR
410 S$ = “         “  (9 spaces)
415 FOR I = 1 TO 48
420 N = RND 7 + 1
425 T$ = MID$(S$, 1, N-1) + “*” + MID$(S$, N+1, 9-(N+1))
430 WAIT 15: PRINT T$
440 NEXT I
445 BEEP 3: CLEAR: END

This is just show a dancing asterisk (*) on the screen.

WAIT 15: PRINT T$:   This causes the string T$ after a quarter of a second.  WAIT operates in 1/60 seconds.

RND n:  This is the random command.  If n = 1, the result is between 0 and 1. 

BEEP n:  This makes the EL-5500 III beep n times. 

Eddie

This blog is property of Edward Shore, 2017.



Retro Review: Halo HLC-1 Lighting Calculator

Retro Review:  Halo HLC-1 Lighting Calculator

HLC-1 Lighting Calculator
Years:  Unknown
Type:  4-Function, Lighting
Memory Registers: 1 (M)
Battery: A76

The Halo HCL-1 is a professional lighting calculator and a standard 4-function calculator. The standard 4-function calculator should be self-explanatory, let’s focus on the lighting part.

The HCL-1 is abundant on eBay, and make sure you get it with the foldout manual because (1) the manual is well written and (2) it explains the process in which pre-programmed calculations are completed.  I will show a short summary of some of the pre-calculations available below.

Trig table from the manual, something we don't see in calculator manuals

Did I mention that the manual contains a short table of sines and cosines?

US units are used (length is measured in feet).

Calculating Room Cavity Ratio:

Input:
Room Width in feet, [ RW ]
Rood Length in feet, [ RL ]
Room Cavity Height in feet, [ H ]

Output:
[ RCR ] calculates the Room Cavity Ratio

The HCL-1 assumes a rectangular room.  The formula:

RCR = (5 * H * (RW + RL)) / (RW * RL)

Footcandle Calculation

Input:
Coefficient of Utilization, between 0 and 1, [ CU ]
Number of lamp lumens, [ LL ]
Required footcandles, [ FC ]

Output:
Press [ CAL ].  If successful, a 0 appears in the display.
[ RCL ] [ NUM ]:  number of adjusted luminaries (lights)
[ RCL ] [ FC ]:  number of adjusted footcandles
[ RCL ] [ A ]:  area that is illuminated
[ RCL ] [ SPG ]:  fixture spacing in feet

I am thinking that this solves where to put ceiling lights on the ceiling in a grid, like in a school classroom or business office.

You can factor in the lamp lumen depreciation factor ( [ LLD ] ) AND luminaire dirt deprecation factor ( [ LDD ] ).

Final Verdict

I am glad to have the HLC 1 in my collection.  It is one of the most unique calculators ever made and was met with amusement when I posted a picture of it on my Instagram account.  Don’t lose the manual. 

Eddie

This blog is property of Edward Shore, 2017

Retro Review: Radio Shack EC-4036

Retro Review:  Radio Shack EC-4036

Radio Shack EC-4036

Radio Shack EC-4036

Company:  Radio Shack
Years:  most likely late 1980s to early 1990s
Type:  Scientific, Programming
Number of Steps: 40
Operating System: AOS (post-script)
Memory Registers: 3 (M, A, B)

Chipset:  Sharp LI3301A


Sharing the Same Chipset

According to a YouTube video from badogember csatornája, the EC-4036’s chip set is Sharp LI3301A which is shared with many other calculators such as the Citizen SRP-145, Citizen SRP-40, and Aurora TB607.  This means that this calculator line up and functions are cloned and marketed by many companies.  (Link to that video: https://www.youtube.com/watch?v=iGX4Mk3gwmM ).  The Logtech LC-604 is also part of this chip subset. 

I am thankfully that the EC-4036 is cloned (or is a clone) because I couldn’t find a manual for Radio Shack online (not even their website has a manual for this particular calculator).  Since the Citizen SRP-145N has the same chipset, its manual will have to do.  (Link:  http://calculator.citizen-europe.com/old-manuals )

There is also a discussion on the Museum of HP Calculators about the Citizen SRP-145 here:  http://www.hpmuseum.org/forum/archive/index.php?thread-6200.html 

A member of the Minimalist Club

The EC-4036 has 40 programming steps.  Furthermore, only simple programming is allowed, as there are no loops, alphabetic characters, or tests.  Unfortunately, the programming is “blind” with no way to step backwards and forwards.  Programming the EC-4036 will require either trust or writing the program down first (I always do the latter).

The good news is that you can be Statistics mode when entering programs and take advantage of the one-variable statistics functions (mean, standard and population deviation, sums Σx and
Σx^2).

There are two functions dedicated to the programming mode:

HALT:    Pauses the calculator and shows the result. This is very handy.  To continue execution, press [COMP].

[ x ]:  I originally though that this is a integer part function.  It is not, this is the Input function.  When an [ x ] is encountered, the calculator asks for a numeric input.  Press [COMP] to continue.

The EC-4036’s program is erased each time you start a new program, but with 40 steps, I image that all the programs for the EC-4036 will be short and will be easy to input when required.

When programming, program like you are actually making a calculation.  This really comes into play when you want insert a prompt step ([x]).  After pressing [x], enter a valid number to continue the calculation.  Planning is definitely a key.

Keyboard

The keys are rubbery and soft to the touch.  Thankfully, the keys are still responsive.

I wish the labeling on some to the keys could be clearer. Here are the mapping of the most confusing looking keys:

[A >A] (CD CAD):
Primary Function:  Recall A.  If a number is entered first, it multiplies it by A. 
Second Function:  Store the number in the display to register A.
Primary Function Stat Mode: Clears the last data point entered
Second Function Stat Mode: Clears all data points

[B >B] (n Σx)
Primary Function:  Recall B.  If a number is entered first, it multiplies it by B. 
Second Function:  Store the number in the display to register B.
Primary Function Stat Mode: Recall n (number of data points)
Second Function Stat Mode: Recall Σx (sum of all data points)

[ MS ] (x-bar Σx^2)  
Primary Function:  Stores the number in register M 
Second Function:  N/A
Primary Function Stat Mode: Recall the arithmetic mean of all data points
Second Function Stat Mode: Recall Σx^2 (sum of all squared data points)

[ MR ] (s σ)
Primary Function:  Recalls the number in register M 
Second Function:  N/A
Primary Function Stat Mode: Recall sample deviation (sx)
Second Function Stat Mode: Recall population deviation (σx)

[ M+ ] (DATA)
Primary Function:  Adds the number in the display to register M 
Second Function:  N/A
Primary Function Stat Mode: Enters the number as a data point
Second Function Stat Mode: N/A

Your Basic Scientific Calculator

The EC-4036 has the basic scientific functions: trigonometric, logarithmic, exponential, hyperbolic, power, factorial, and decimal/degrees-minutes-seconds conversion.

When the [2ndF] and HYP is evoked, the 2F and HYP indicators take the display.  For some reason I like this. 

Final Verdict

A nice collector calculator to have.  I wouldn’t pay a large amount of money for it however, I paid about $6.  If you like a small programming calculator or a challenge, this is one to consider.

Now for a few sample programs.

EC 4036 Program:  Percent Change

Input: 
[COMP] new [COMP] old [COMP]

Δ% = ( [1] – [2] ) / [2] * 100

Program:
[ x ]  (enter a valid number)
-
[ x ]  (enter a valid number)
MS
=
÷
MR
*
100
=
HALT

Example:  new = 52, old = 50.  Result:  Δ% = 4

EC 4036 Program: Convert from Rectangular to Polar Coordinates

This converts rectangular coordinates (A, B) to polar coordinates (limited).

r = √(A^2 + B^2), θ = atan(B/A), -90° ≤ θ ≤ 90°

Program:
[ x ]  (enter a valid number)
[ 2nd ] [ A >A ]  (store in register A)
x^2
+
[ x ] (enter a valid number)
[ 2nd ] [ B >B ] (store in register B)
x^2
=
HALT  (display r)
1
[B >B]  (recall B*1)
÷
1
[A >A] (recall A*1)
=
tan^(-1)
HALT   (display θ)

Example:  A = 3.5, B = 3.0. 
Results:  r = 4.609772229, θ = 40.60129465°, 0.708626272 radians


EC 4036:  Circumference and Area of a Circle

This program stores radius in register A and calculates the circumference and area of a circle.  Here I demonstrate the multiplication feature of [A >A].

Circumference = 2*π*r, Area = π*r^2

Input:  radius [COMP] display circumference [COMP] display area

Program:
[ x ]  (enter a valid number)
[ 2nd ] [ A >A ] (store in register A)
*
2
*
π
=
HALT (display circumference)
π
[A >A]  (multiply π by register A)
[A >A]  (multiply A*π by register A)
=
HALT (display area)

Example:  r = 5.45. 
Results:  Circumference = 34.24335992, Area = 93.31315579

This blog is property of Edward Shore, 2017

Friday, January 13, 2017

Retro Review: Sharp Compet CS-2302 Review

Retro Review:  Sharp Compet CS-2302 Review

I’m going for a little departure from the usual types of calculators I cover.

Sharp Compet CS-2302


Company:  Sharp
Type:  Adding Machine, Paperless
Years Made: 1970s
Batteries:  AC Plug

I purchased the Compet CS-2302 from a local thrift store in Glendora, CA back in the summer of 2016. 

Adding machine, but where’s the tape?

The CS-2302 is a paperless desktop calculator, but retains the characteristics of an adding machine.  That is to add numbers, enter your number and press [ + = ].  The total is immediately displayed.  Same with subtraction, press [ - = ] to subtract. 

What is unusual about the CS-2302 is a lack of a subtotal or total key (normally marked [ S ] and [ * T ], respectively).  Totals are cleared by pressing the clear button twice.

There is an exchange key [ ↕ ] on the CS-2302, something I don’t ever recall seeing on an adding machine.

The CS-2302 has two memories, M and I.  There are separate memory add and recall keys dedicated to both memories.

The keyboard is very solid.  The keys are responsive and it was well maintained. 

The Very Bright Display

The CS-2302 in a dark room

I think the CS-2302 wins the award for having the brightest display when it comes to calculators. 

The Red Negative Indicator

Even more amazing is the multi-color display.  Yes, in 2017 we live in a world where multi-color displays on calculators are close to common place:  HP Prime, TI-84 Plus CE, TI-nSpire CX, Casio Prizm, and Casio Classpad fx-CP400.  However, the CS-2302 is from the 1907s: a red negative sign indicator

Modes

The usual adding machine modes are present:  Constant Mode toggle (K), fix decimal selector complete with Add Mode, and automatic summation (Σ) toggle.

If you are not familiar with Add Mode, it is a mode where the all sums are rounded to 2 decimal places.  You are allowed to add and subtract numbers in dollars and cents without having to press the decimal point key [ . ].  Add Mode is a favorite of many office workers.

Item Counts, AVG, MU

The Item Count adds the number of addition and subtraction operations.  Pressing [IC] gives the item count and twice to clear it.

You can also use the item count to get the average of numbers added by one step with the average key ([AVG]).  Calculating the average clears the item count automatically.

Sharp called the [MU] the multiple use key in the 1970s.  Now the key is called the mark-up key.  It is true that [MU] serves multiple purposes.  Looking at the manual from similar desktop calculators from Sharp, the [MU] allows for cost, sell, markup, margin, and percent change calculations. For example:

Percent Change:  new [ + ] old [ - ] [ MU ]

Selling Price:  cost [ ÷ ] margin [ MU ]

Markup:  sell [ + ] cost [ - ] [ MU ]

Final Verdict

I love the display of the CS-2302 and the big size and steady keyboard.  I wish the CS-2302 had a totals key [ * T ] to complete calculations.  This desktop calculator, and others like it, would be a good ecological alternative for those who don’t want paper tape. 

Eddie

This blog is property of Edward Shore, 2017



Thursday, January 12, 2017

Retro Review: Sharp Scientific Computer EL-5500 III

Retro Review:  Sharp Scientific Computer EL-5500 III

Company:  Sharp
Type:  Scientific, BASIC
Years Made: 1985 - 1991
Batteries:  2 CR-2032 batteries
Memory/RAM: 6,878 bytes




Basic Features

The EL-5500 III operates in two main modes:  CALC (calculator) and BASIC (programming mode).  The CALC mode has two additional sub-modes:  Matrices and Statistics (Linear Regression).   You can also convert numbers between Decimal (base 10) and Hexadecimal (base 16). 

The matrix mode uses RAM and has two matrices in storage: X and Y.  Thankfully, Sharp printed matrix operations on their hard case, includes arithmetic, scalar arithmetic, inverse, squaring, transpose, and determinant.  Given how the EL-5500 III has was released over 30 years ago, I image someone has come up with a good program to find eigenvalues.   X not only serves an input matrix but an output. With the one line screen, elements are shown one at a time.

In CALC mode, calculations are in AOS mode (algebraic, with the one-variable argument functions such as the logarithmic and trig functions are executed after the number is entered), and the equals key ( [ = ] ) completes operations.  However, in BASIC mode, calculations are entered the way they are written, and they are completed when the [ ENTER ] key is pressed.

For example:  to calculate log(6):
CALC Mode:  6 [ log ]
BASIC Mode:  [ log ] 6 [ ENTER ]

There is no built-in complex number mode.

The Keyboard

The keys are small, but no so small that I don’t have to use a stylus or aid to press them.  The keys are easy to the touch.  I am also impressed on how light the keyboard is, which is impressive for 1980s portable keyboard. Yet the keyboard is steady and the keys give a solid response.  Sharp did a great job with this model.

Programming

As mentioned before, the EL-5500 III has 6,878 bytes, somewhat comparable to the TI-74.  Also similar to the TI-74, there is only one program space.  You can fit multiple programs in the EL-5500 III as long as you organize your line numbers correctly.  However, the EL-5500 III has definable keys with the following available labels: A, S, D, F, G, H, J, K,L, ‘, Z, X, C, C, V, B, N, M, SPC. 

To label a program, follow this format:

Line number  “key” : command
END

Use the [DEF] key to run labeled programs. 

The EL-5500 III has a beep sound (via BEEP command).  I think am I going to start using beeps in programs when I can. 

The ability to type lower case is present through the [SML] which toggles lower case on and off.

The classic mathematical BASIC commands are available:  DELETE, NEW, GOTO, STR$, VAL, DATA, READ, DIM, FOR loops, IF tests, GOSUB, INPUT, PRINT, ON GOTO/GOSUB, and the almost completely unnecessary LET.

LIST is used instead of FETCH.

FOR loops:
FOR var = starting value TO ending value [ STEP increment ] … NEXT var

IF tests:
IF conditional test THEN do this one command if test is true
IF conditional test THEN go to this line number (no GOTO is necessary)

LET assigns a value to a variable.  However it is not required.  For example, both statements listed will store 5 to the variable A:
LET A = 5
A = 5

Strings are concentrated with a plus sign while multiple commands can be stringed together with a colon.

Line numbers are needed to organize the statements.  I wish line numbers were brought back in modern calculators that used basic.   According to the EL-5500 III manual, the available line numbers range from 1 to 65279.

Most commands also have short cut keywords.  For example, RAD., RADI., and RADIANS set radians mode, while P. and PR. can both be used for PRINT.  When entered, the EL-5500 III will complete the abbreviations with their full word counterparts.  This was created to save time.

Accessories

The EL-5500 III can be attached to a CE-126P, a combination thermal printer and cassette player interface.  Yes, the CE-126P can be connected to a compatible cassette tape player, which the player is used to record programs.     

Final Verdict

The EL-5500 III is a pleasure to hold and use.  Despite the screen being small, the text on the screen is crisp and easy to read.  The most likely place to find EL-5500 III computers for sale is eBay, which is where I purchased mine.  Prices do vary, I paid $38.  I didn’t get any accessories though.  I recommend buying one if you are interested.  

Programs using the EL-5500 III to come in the future (along with my beloved HP 71B).

P.S. The EL-5500 III is not the calculator/computer used in the 1984 movie Ghostbusters.  That was the Radio Shack TRS-80 PC-4.  (http://www.gbfans.com/equipment/other/radio-shack-pc-4-calculator/ )

Eddie

This blog is property of Edward Shore, 2017